1. Field of the Invention
The present invention relates to alloy-semiconductor radiation detectors with rectifying junction contacts, the formation of rectifying junction contacts on alloy-semiconductors using photo-electrochemical etching, the use of such alloy-semiconductor devices with rectifying junction contacts in PIN ionization detector devices, and systems and methods for revealing surface morphology of such alloy-semiconductors.
2. Description of the Related Art
Several methods have been developed for the external formation of P- and N-type contacts on CdTe and CdZnTe for Positive-Intermediate-Negative (PIN) devices. For example, X. Li, et al., “Effect of nitric-phosphoric acid etches on material properties and back-contact formation of CdTe-based solar cells,” Journal of Vacuum Science Technology A, 17(3), May/June, 1999; R. Sudharsanan et al., “Fabrication and characterization of CdZnTe radiation detectors with a new P-I-N design,” presented at the 1996 U.S. Workshop on the Physics and Chemistry of II-VI Materials, 1996; A. Khusainov et al., “Performance of a high resolution CdTe and CdZnTe P-I-N detectors,” Nuclear Instruments and Methods in Physics Research A, 380, 245–251, 1996; T. Narita et al., “Development of prototype pixellated PIN CdZnTe detectors,” Proceeding of the SPIE, 3446, 1998; S. U. Egarievwe et al., Proceeding of SPIE, 3768, 1999; T Narita et al., “Development of IMARAD CZT detectors with PIN contacts,” Proceeding of SPIE, 3768, 1999; M. Niraula et al., “Fabrication of CdTe detectors in a P-I-N design for gamma-ray spectroscopy,” Proceeding of SPIE, 3768, 1999; M. Niraula et al., “Fabrication and performance of P-I-N CdTe radiation detectors,” Nuclear Instruments and Methods in Physics Research A, 436, 132–137, 1999; and T. Takahashi et al., “High-resolution Schottky CdTe diode for hard X-ray and gamma-ray astronomy,” Nuclear Instruments and Methods in Physics Research A, 436, 111–119, 1999, all describe various methods for forming an external P-type and/or N-type contacts on CdTe and CdZnTe for PIN semiconductor devices.
However, all these methods suffer from several shortcomings. First, these conventional methods all involve sophisticated vacuum deposition equipment. This necessarily entails that production of semiconductor devices using such methods are expensive and difficult. Second, these conventional methods also require high temperature heating during formation of the contacts, which heating can cause degradation of semiconductor's material properties. Third, because the metal used in the metal deposition process may be impure, the semiconductor device can become contaminated during the metal deposition process. Fourth, it is possible that the interface between the deposited metal and semiconductor device may have an oxide layer that can degrade device performance. Thus, there remains a need for an improved system and method for forming rectifying junction contacts in PIN alloy-semiconductor devices. There also remains a need for a PIN ionization detector device utilizing such alloy-semiconductor devices with rectifying junction contacts. Further, there remains a need for an efficient and inexpensive method for revealing surface morphology of alloy-semiconductors. These advantages have been obtained with the present invention.